1. Field of the Invention
The present invention relates to an apparatus provided in a construction machine, such as a hydraulic excavator, equipped with an engine and an engine room, to release exhaust gas of the engine and air having been used for cooling, to an outside of the engine room.
2. Description of the Background Art
The background art will be described by taking a hydraulic excavator as an example.
A typical hydraulic excavator comprises a crawler-type lower traveling body, an upper slewing body mounted on the lower traveling body in such a manner as to be slewable about an axis perpendicular to a ground surface, and a work attachment attached to the upper slewing body. An engine room is provided in a rear end region of the upper slewing body, and, in the engine room, an engine and its related devices (a cooling fan, a muffler, a heat exchanger, etc.) are installed.
This type of hydraulic excavator is provided with an apparatus for releasing, to an outside of the engine room, exhaust gas from the engine and exhaust air, that is, air having been sucked into the engine room by the cooling fan and used for cooling of the heat exchanger and the like. A heretofore-known example of this apparatus is disclosed in JP 03-229907A (Patent Literature 1).
FIG. 8 shows a technique disclosed in the Patent Literature 1. FIG. 8 is a schematic diagram of an engine room 1, when viewed forwardly from therebehind. The engine room 1 accommodates an engine 2, a cooling fan 3 configured to be driven by the engine 2, and a heat exchanger 4 such as a radiator. The engine room 1 includes an engine cover which covers the engine 2 from thereabove, an air suction port 5 and a gas release port 6. The fan 3 and the heat exchanger 4 are disposed in adjacent relation to a first one of opposite axial ends of the engine 2. The air suction port 5 and the gas release port 6 are provided in regions of the engine cover on the side of the first axial end and on the side of the other, second, axial end, respectively. The fan 3 is configured to be rotated to thereby perform: introducing outside air through the air suction port 5; making the introduced air pass through the heat exchanger 4; and releasing the air having been used for cooling, namely, exhaust air, through the gas release port 6.
A muffler 7 is provided at the second axial end of the engine 2, and exhaust gas discharged from the engine 2 is released to the outside via the muffler 7 and a tail pipe connected to muffler 7, namely, exhaust-gas pipe 8. This exhaust gas, having a high temperature, may deteriorate a surrounding temperature environment if being directly released through the exhaust-gas pipe 8 to the outside. Moreover, the direct release of exhaust gas and exhaust air makes leakage of operating noise, such as engine noise, exhaust gas noise and exhaust air noise, be significant.
For the above reason, the hydraulic excavator using the above heretofore-known technique additionally comprises a tubular-shaped duct 9 shown in FIG. 8. The duct 9 is disposed inside the engine room 1 at a position beneath the gas release port 6, in such a posture that the duct 9 vertically extends and upper and lower ends thereof are opened to the gas release port 6 and the inside of the engine room 1, respectively. Besides, the exhaust-gas pipe 8 has a distal end portion, which is inserted into the duct 9 so as to extend upwardly to serve as an ejection pipe 8a, allowing exhaust to be ejected from an opening of the distal end of the ejection pipe 8a into the duct 9. The thus ejected exhaust gas is mixed with exhaust air within the duct 9. This enables the exhaust gas released to the outside to have lowered temperature and enables operation noise to be reduced in the duct.
However, the intensive ejection of exhaust gas from extremely restricted area, namely, the distal end opening of the upwardly-extending ejection pipe 8a, causes efficiency of mixing between exhaust gas and exhaust air to be deteriorated, thus suppressing a drop in temperature of the exhaust gas. Besides, the straightforward ejection of the exhaust gas from the distal end opening of the ejection pipe 8a toward the gas release port 6 does not allow a significant effect on reduction in exhaust gas noise through the duct 9 to be expected.